The present invention relates to a mouthpiece which can be exclusively used by a specified user and which can protect jaw bone, teeth, and an oral cavity from external force properly in view of moldability, flexibility, and elasticity. The present invention further relates to a method of producing such a mouthpiece as described above in a simple manner.
Conventionally, in such an contact sport such as rugby football or the like, an accident, for example, fracture of jaw bone, a laceration of soft tissue of an oral cavity, or the like, has frequently happened. Accordingly, in order to prevent such an accident, it is desired to put a mouthpiece in a mouth. Further, a mouthpiece has been used as a medical instrument for preventing gnashing, for treating temporomandibular disorders, or the like. Such a mouthpiece is formed by a rubbery elastic material as described, e.g., in Japanese Patent Application (OPI) No. 100273/86 (the term "OPI" used herein means a published unexamined Japanese patent application).
Such a mouthpiece formed of a rubbery elastic material, however, has a disadvantage in that the mouthpiece has not a sufficient impact absorption effect and that it is difficult to perfectly fit the mouthpiece in a mouth. That is, since a rubber material used, mouthpieces are poor in moldability, and since it is impossible to easily make moldings for exclusive use for specified users, a mouthpiece which is satisfactorily good in condition in use and which is satisfactorily proper in flexibility as well as in elasticity has not been obtained although some improvements have been proposed as described, e.g., in U.S. Pat. No. 3,073,300.
Generally, such a mouthpiece as described above is produced in such a manner as follows. First, an impression of teeth of an objective user is modeled by using a dental impression material, such as an alginate impression material, so as to form a plaster cast of the teeth, and a thermoplastic elastic rubbery elastic material shaped into a plate having a thickness of about from 1 to 3 mm is softened by heating and applied to the plaster cast to thereby obtain a mouthpiece through a vacuum molding process. Being molded with such a rubbery elastic material shaped into a plate even in thickness in all portions, the mouthpiece is also even in thickness in portions corresponding to a front teeth portion and a molar teeth portion, or has such a condition that the portion corresponding to the front teeth portion becomes thinner upon molding than the portion corresponding to the molar teeth portion because the front teeth are shaper than the molar teeth, so that there is a tendency that occlusion force at the molar teeth portion is exceedingly larger than that at the front teeth portion occluding.
In normal occlusion, however, a space between the front teeth portions of upper and lower jaws immediately before occlusion is about twice as wide as that between the molar teeth portions of the upper and lower jaws, so that occlusion force at the molar teeth portion is larger than that at the front teeth portion. Accordingly, there is a disadvantage in that strain may be generated in jaw bone or temporomandibular joint in the case where a mouthpiece is put in a mouth rather than the case without a mouthpiece.
It has been therefore desired to provide a method of producing a mouthpiece having a thickness which is larger at a portion corresponding to a front teeth position than at a portion corresponding to a molar teeth position.